A psychrometric chart is a graphical representation of the psychrometric processes of air. These processes include properties such as dry bulb temperature, wet bulb temperature, humidity, dew point, and more.
I know this wasn't really its intended purpose, but I'm actually watching this video for my chemical engineering thermodynamics class haha. Great explanation!
Taking HVAC as an elective for my mech eng bachelors. I have a test in 20 mins and Im prepared but sometimes I mix up the lines in my head as the chart was shown to us recently. Thank you for making it clear and consice :)
After watching endless of RU-vid videos about this topic, I finally found this one which in all honesty is the most clear explanation about this chart, thanks to all the people who work on it so hard
Yes this guy is good at explaining propertys of air. When i went to the construction college for pre exam prep 2 years they did convey all this info but not as well. Weird thing as a HVAC contractor for ten years I only knew a small few who would use this kind of data when sizing a system for residential homes, then a change with B&Z required it and they were lost for quite a long time they had to learn manual j and D to draw a plan. I made quite a living during these periods.
I don't work in HVAC but im taking a MechE course right now that discusses this. Been having trouble reading this chart via textbook, so this lesson was perfect, thanks so much!
I am in my second year of my architecture degree and I have a course dedicated to mechanical, electrical and plumbing in commercial buildings. We started looking at these charts the other day and I was so lost. Thank you so much for this video, it helped so much! You are the best. Thanks!
Great. Would be nice, for some, to start at Relative Humidity section (~6 minutes) , and note the nice big fraction shown in the top left blank area of the chart, and notice that on any vertical 'dry air' temperature line the relative humidity is in nice linear 'tick marks' (going from zero to 100% saturated). And that the way we shift from the current point out to the 'web bulb' (diagonal line) is neatly at right angle to the curves of the relative humidity..
I thinks I got it. In a nutshell: Given a Pchart for a specific barometric pressure, the intersection of any two parameter values is a single point on the Pchart. Given a point on the Pchart, all its parameter values on the Pchart can be easily determined. Thks TomB
Great video! Thank you for sharing this information. What's the model number of that Fluke device? I'm interested in getting a digital humidity/temperature meter as precise as possible? I've noticed how the measurements on the sling might be biased by how consistent the person using it is while rotating it, so a digital one could be a solution. Thanks again.
We have not made a short video series, but we do have a 3 hour free training on the Psych chart that does cover that and more. Here is the link to the first 90 minute module of that training - register.gotowebinar.com/register/1045518315942376460
I noticed the line coming into the compressor inside the condensing unit has few inches of rubber hose left on it, rest of line is exposed? Is this line going to sweat in the summer, is it going to affect the performance if I don’t replace the broken insulation? And why? Thanks
If... or rather when... that line gets below the dewpoint of the ambient air, it will sweat. Yes, missing insulation affects performance, which is why it was originally insulated. A small amount of insulation missing might not affect it much. The more that is missing, the more the customer may notice a higher energy bill or less cooling capacity.
At 8:02 why don’t we have a problem when we lower humidification to 20% since that reduces the dew point temperature? I thought condensation occurs when you go below dew point temperature?
Condensation will occur when the dry bulb air temperature of surface in question drops below the dewpoint. In this example, the indoor temperature is fixed at 75F and the window temperature is fixed a 35F. We started with air at 75 db, 23% RH, and 35 dewpoint. We changed the indoor humidity down to 20% so that puts us at 75 db and 31 dewpoint. If you lower the RH (23 down to 20%) with a fixed dry bulb temp (75F), then the dewpoint of the air is lowered to 31. If my window surface is 35 db and my indoor air is 31 dp, then my window is ABOVE my dewpoint and hence no condensation.
Ryan, I have a question but here's the context 1st: I have force air conditioning for the whole house. But on a whim I ran my portable a/c on dehumifier mode the last few days. !Amazingly it was getting a gallon of condensating a hour! More importantly although the temp was pretty hot, the humidity was pretty comfortable ~%70. It was like being out in the arizona desert in the summer (hot but dry). In a nutshell I want a lot more dehumidified air & a loot less cool air. In the portable a/c unit I assume air is slowly forced over just above freezing evaporator coil thus maxing the dwell time for condensation. Finallllllllllly the question: ?Can I buy a thermostat that will make my whole house force air conditioner be more of a dehumidifer? If not, how can I do it myself?
Yes, lots of thermostats use the air conditioner to run a dehumidification mode. This would include some of my favorites, such as ecobee 4 (or 5), Carrier "original" Cor, and Bryant Housewise. Also many stats from Venstar and Honeywell. There are two ways in which these can be used. 1) Cool to Dehumidify: this forces on the Y1 signal if the space is more humid than the dehumidification setpoint... even if the space temp is satisfied. This works with all equipment irregardless of type or brand. 2) Dehumidification Mode of the Equipment: this would turn on the dehum relay of the stat as needed. This relay would be wired to the DH or DEHUM input on the furnace. This will slow the blower down while running the cooling to change the sensible heat ratio and hence optimize the dehumidification ability. It should be pointed out that both of these are different than running a dehumidifier. A dehumidifier is a essentially an air conditioner with one important difference. Both the evaporator coil and the condenser coil are in the occupied space. This means no heat is rejected to the outdoors and instead it is rejected back into the space. This is obviously not energy efficient. Additionally, it does not lower the indoor space temp. So a dehumidifier only dehumidifies, but an air conditioner can cool and dehumidify... and how the stat controls it can help it do one more than the other.
@@TECTubefilms How to set humidity on NEST ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-7YTk_AzJ6fg.html Nest Thermostat - How To Set Up a Fan Schedule ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-K4uuIbwLw5w.html
That example was 30% RH in the building at the humidistat, not 30% at the cold surface and the point of condensation. In that section of the video we were explaining how the cold window would drop the temperature of the air immediately next to the window (say within an inch of the surface) and as that temp dropped, the RH would rise. As it gets cold enough to raise the RH to 100%, then condensation occurs.
Back when the video was made you used to be able to get them online from the Carrier Bookstore, but they closed that site. You can, however, still get them from your local Carrier distributor.
Would this help ? >> [www.google.com/url?sa=t&source=web&rct=j&url=www.ashrae.org/File%2520Library/Technical%2520Resources/Bookstore/UP3/SI-1.pdf&ved=2ahUKEwj02oyn0YruAhVL7XMBHUtwARAQFjAAegQIARAB&usg=AOvVaw0bMgvpCZtGI6bOrFbE3gmO]
